This invention relates in general to electronic mail (e-mail) systems and, more specifically, to processing unsolicited e-mail distributed in bulk.
Unsolicited e-mail distributed in bulk, sometime referred to as Spam™, is the scourge of the Internet community. It is not uncommon for a user to receive ten to fifty unsolicited e-mail messages per day. Studies have shown that ten percent of all e-e-mail traffic on the Internet is unsolicited bulk e-mail. A sender of unsolicited e-mail can purchase a list of millions of e-mail addresses from a list broker and easily distribute a message to the list for little or no cost. The cost of the unsolicited e-mail is paid by the providers of the Internet backbone and the users who pay access charges to download their e-mail. The senders of unsolicited e-mail offer services such as how to get rich quick, how to loose weight fast, hot stock tips, various pornographic web sites, and other shady “opportunities.”
Preventing unsolicited e-mail from annoying users is a burgeoning industry. Internet service providers (ISPs) and e-mail application service providers (ASPs) experience subscriber attrition that is attributable to excessive amounts of unsolicited e-mail. For example, a user may switch to other ISP or e-mail ASP to experience a temporary reprieve from unsolicited e-mail. Unfortunately, the reprieve only lasts until the list brokers harvest the new e-mail address of the user.
Technology used to combat the efforts of unsolicited e-mailers is an ever-escalating arms race. The ISPs and e-mail ASPs will develop a new technology for detecting unsolicited e-mail broadcasts and the unsolicited e-mailers will develop techniques that renders the new technology ineffective. For example, once an unsolicited e-mail message is identified, the ISPs and e-mail ASPs search for other messages with the exact subject and block those messages. To combat this, the unsolicited e-mailers often attach a changing tag to each subject such that no two subject lines are the same in a large unsolicited e-mail broadcast. As those skilled in the art appreciate, more sophisticated techniques for detecting and blocking of unsolicited e-mail are desired.